This Nonprovisional application claims priority under 35 U.S.C. § 119(a) on patent Application No. 2002-333705 filed in Japan on Nov. 18, 2002, the entire contents of which are hereby incorporated by reference.
The present invention pertains to a sensor, and in particular to an automatic door sensor.
Conventional automatic door sensors (hereinafter “sensors”) detect a person or other object headed toward an automatic door and cause the automatic door to open and/or close.
Conventional sensors include, for example, sensors such as that shown in FIG. 13, in which this sensor 1 is disposed above an automatic door D, protected zone(s) intended for detection being irradiated with light from light-projecting element(s) (not shown), this irradiated light being reflected at protected zones A (A11, A12, A13, A14) and being incident on and received by light-receiving element(s) (not shown), with presence and/or absence of object(s) being detected based on the amount of light received.
Now, given protected zone(s) A11 proximate to sensor 1 and protected zones A12, A13, A14 distant from sensor 1 (in direction(s) Y), it so happens when this sensor 1 is used to detect presence and/or absence of object(s) that the characteristics of light cause zone extent to increase as one goes from protected zone(s) A11 proximate to sensor 1 to protected zones A12, A13, A14 distant from sensor 1 (in direction(s) Y). This being the case, it may sometimes happen, as shown in FIG. 13, given a plurality of protected zones A alongside automatic door D, that zone(s) A19, at which detection cannot be carried out, will appear between protected zone(s) A11 proximate to sensor 1 and automatic door D, the sensor failing to respond to movement of object(s) at such zone(s) A19.
Sensors capable of detecting the foregoing zone(s) A19 proximate to sensor 1 at which detection might otherwise be impossible have therefore been developed, such sensors including, for example, the sensor described at Japanese Patent No. 2871494.
The sensor described at Japanese Patent No. 2871494 is such that projected beams irradiated from a light-projecting element pass through a lens to irradiate protected zones alongside a door, reflected beams from such protected zones being condensed by way of a lens and being monitored at a light-receiving element so as to permit detection of presence and/or absence of object(s). At this sensor, a slit for regulating the projected beams and reflected beams is disposed in intervening fashion between the lens and the light-projecting and light-receiving elements, and the protected zones are given cross-sectional shapes partially approximating the more or less linear region alongside the surface of the foregoing door.
In this sensor, projected beams irradiated from a light-projecting element pass through a lens to irradiate protected zones alongside a door, reflected beams from such protected zones being condensed by way of a lens and being received at a light-receiving element. Because the aforementioned protected zones are given cross-sectional shapes partially approximating the more or less linear region alongside the surface of the aforementioned door, it is possible to cause the protected zones to closely approach the door surface.
However, with the sensor described at this Japanese Patent No. 2871494, presence of the slit which regulates the projected beams and the reflected beams makes efficient use of the projected beams impossible. That is, since the effect of blocking of light by the slit which is provided between the lens and the light-projecting and light-receiving elements is being utilized for protected zone shape, focal length must be chosen based on this slit itself; and since the amount of light that is produced which corresponds to the portion of the beams that is blocked by the slit goes to waste, it is impossible to achieve low operating cost.
Furthermore, with respect to the light irradiated by the sensor, it is preferred that the light-projecting and light-receiving elements be disposed at the focus of the lens. However, with the sensor described at this Japanese Patent No. 2871494, if the light-projecting and light-receiving elements are disposed at the focus of the lens this will result in blurring of the extents of the protected zones irradiated by the slit, and it will be impossible to cause the aforementioned protected zones to be given cross-sectional shapes partially approximating the more or less linear region alongside the surface of the door.
In order to solve one or more of the aforementioned problems, it is therefore an object of the present invention to provide a sensor making efficient use of light at light-projecting and/or light-receiving element(s) disposed at location(s) of focus or foci of lens(es) and/or other such condenser member(s); such that when carrying out detection with respect to protected zone(s) alongside light-projecting and/or light-receiving element(s), edges, on side(s) toward light-projecting and/or light-receiving element(s), of a plurality of protected zones alongside such light-projecting and/or light-receiving element(s), are formed so as to be collinear; and such that protected zone(s) nearest to such light-projecting and/or light-receiving element(s) serves or serve as protected zone(s).